Directional aerial array



Feb. 10, 1942. J. J. B. LAIR 2,272,611

DIRECTIONAL AERIAL ARRAY Filed June 14, 1939 2 Sheets-Sheet l Tranmz'ffer /n mentors i116. [air y 6- 5 M flermux Feb. 10, 1942. J. J. B. LAIR m-AL 2,272,611

DIRECTIONAL AERIAL ARRAY Filed June 14, 1939 2 Sheets-Sheet 2 [Q-Radfa fing Sysfem Guiding Axis Fig. 5.

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Inventors Attom Patented F eb. 10, 1942 STTES r OFEME DIRECTIONAL AERIAL ARRAY York, N. Y.

Application June 14, 1939, Serial No. 279,026

In France June 14, 1938 2 Claims.

The present invention relates to antenna systems and more particularly to antenna systems adapted to be used for radio guiding of vehicles.

One object of the invention is to provide means for producing successively in time interlocking or tangential radiation diagrams which are suitable to guide a vehicle along one or more paths, and in which only two radiating elements are employed.

Another object of the invention is to provide means for the suitable and periodic modification of the phase relationship of the fields from the two radiating elements or two groups of radiating elements fed so as to produce successively in time interlocking or tangential radiation diagrams which are suitable for the radio guiding of a vehicle.

In accordance with one of its features, the invention provides directional systems comprising two radiating elements or groups of radiating elements, the elements of each group being adapted to produce a directional radiation, the said two elements or groups of elements being placed apart at a fixed distance suitably chosen for the production of one or more directional axes, and permanently fed with exciting currents at radio frequency with a fixed phase-relationship chosen with respect to the distance between the two elements or groups of elements and means to produce alternately positive and negative dephasing with respect to the fixed phase relationship between the exciting currents.

In accordance with another feature the invention provides directional systems comprising two radiating elements or groups of radiating elements, the elements of each group being arranged to produce a directional radiation, said two elements or groups of elements being placed at a fixed distance apart which is suitably chosen for the production of one or more directional axes and permanently fed by exciting current of radio frequency, with a phase relationship chosen with respect to the distance between said elements or groups of elements, the phase relationship being periodically modified so as to produce a combination of tangential or interlocking radiation diagrams successively alternating in time to obtain one or more directional axes.

In accordance with another feature of the invention, one of the groups of radiating elements is provided with means for producing such alternate positive and negative dephasing.

In accordance with another feature of the invention, the other group of elements is then provided with means of adjustment of the exciting current strengths such as resistances or reactances.

In accordance with another feature of the invention, the two groups of radiating elements are both provided with means for modifying the initial phase relationship and means of adjustment of the exciting current strengths such as resistances or reactances.

In accordance with another feature of the invention, such alternate dephasing is obtained by modifying the transmission line feeding one of the groups of elements, the two groups of elements then having identical dephasing between the feed voltage and the circulation current, this dephasing being preferably, but not necessarily,

zero.

According to another feature of the invention, the alternate dephasing is obtained by varying the reactance or impedance of a radiating element or group of radiating elements, for example, by means of an additional reactance alternately rendered effective and ineffective in the antenna by means of a relay device.

In accordance with another feature of the invention, the antenna systems embodying the above features are adapted to provide a unidirectional guiding axis.

In accordance with another feature of the invention, antenna systems embodying the above features are adapted to provide a plurality of convergent guiding axes, for example, two, four or more axes.

In accordance with still another feature of the invention, the alternate dephasing is chosen of such value with respect to the other values of the system that the guiding channel obtained is of the desired narrowness.

In a particular embodiment of the invention, the radiating elements consist of two single conductors spaced from each other at a distance equal to half the operative wave-length, and having an initial dephasing equal to 71'. It is, however, clear that this embodiment, given in more detail on account of its simplicity, is not limitative and that numerous networks of directional aerials incorporating characteristics of the invention may be obtained with simple conductors, or sets of conductors, of which the spacing and phase relations are chosen so as to ensure the particular directive properties desired, in order, for example, to increase the precision of guiding along a single axis, to concentrate the energy in a narrower dihedron, or to avoid radiation in a particular direction, or for other purposes which through not solely, suitable for operation with short waves.

In attaining this object in accordance with another feature of the invention, the two directional antennae or groups of directional an Fig. 8 shows the utilisation of the aerial system shown in Fig. 5 in a seaport.

Referring to Fig. 1, two antennae AI and A2 are shown spaced at a distance equal to half an operative wave-length, and radiating in phase opposition. The curves of equal field of the radiation diagram of this set of antennae are of the shape shown in Fig. 2, that is, they have an axis y, y of zero radiation in a direction perpendicular to the plane containing the antennae. These two antennae are shown fed by means of a crossed line L, itself fed at its electrical mid- 1 point by a transmitter E, but it is clear that this tennae are fed. by means of a cable transmission line which may or may not pass through the source of high frequency supply, and are spaced in such a way that between them there is a vehicle-guiding path free from any materialobject.

In accordance with another feature of th invention, these two groups of aerials are connected by a cable transmission line the electrical length of which is brought to a desired relation with the distance between said antennae or groups of antennae by means of one or more networks or an artificial transmission lin connecting the groups of antennae either with each other or with the high frequency source.

In accordance with another feature of the invention the initial phase relationship between the two antennae or groups of antennae may be modified as desired by modifying this artificial line, or lines so as to displace angularly the directiv axis and to balance it in all desired directions merely by adjusting these artificial lines.

In accordance with another feature of the invention, the modification of the initial phase relationship between the two radiating elements, or groups, for example, alternately positive and negative dephasing with respect to said initial 1 phase relationship is obtained by modifying the electrical length of the transmission line supplying the groups of antennae, this modification being made by means of the artificial lines or net- ,works inserted in said transmission line, or on a part of this network. This modification of the phase relationship might also be obtained as indicated hereinbefore by modifying the trans-' mission line itself or the electrical length of the radiating elements.

In accordance With still other features of the invention, th two antenna systems may comprise either combinations of frame aerials and vertical antennae or rather one of the two systems only may comprise two or more frame aerials, and the other system one or more radiating conductors.

The invention will be explained in detail in the following description in conjunction with the attached drawings, in which:

Fig. 1 represents a set of antennae radiating in phase-opposition;

Fig. 2 represents an example of a radiation diagram obtained with the system of Fig. 1;

Fig. 3 shows an example of radiation diagram obtained with a system of aerials incorporating characteristics of the invention; and I Fig. 4 shows an example of an arrangement of aerials incorporating characteristics of the invention;

Figs. 5 and 5 show schematically two examples of directional antenna systems incorporating features of the invention;

Iii)

arrangement is only given as a simple form of directive network supplying diagrams arranged to give guiding axes.

vi If th phase differences of the radiations of the two antennae Al and A2 is increased by a certain angle or. and becomes, for example 1r+a instead of 1r the direction of zero radiation y, y is modified as shown in Fig. 3 and each semiaxis 0y, 0y is turned through such an angle ,8 that the relation 1 21% COS {3 =0:

is fulfilled, (1 being the distance between the two antennae AI and A2 A being the wave length. As,in the case under consideration, this distance is equal to half an operative wave-length, we have:

andthe resultant diagram is that shown in solid lines in Fig. 3.

By producing, in, accordance with the invention, alternative dephasings of value oi and +0: the resultant diagram will be an interlocking of the two corresponding radiation diagrams successively in time one diagram being shown in solid lines and the other in dotted lines in Figure 3. This double diagram will supply an effective guide along the axis y, y of Fig. 3 in accordance with the known methods.

Such alternative dephasing obtained from a fixed initial dephasing between the antennae may be obtained in various ways, and the invention provides means for carrying out such alternate dephasing from an initial dephasing chosen in relation tothe spacing of the two antennae or radiating units employed.

Such dephasing'may be obtained in the first place by Varying the electrical length of the line feeding one of the antennae, for example, Al, the conditions of feeding of the other antenna A2 remaining unchanged. The dephasing in this case is imposed on the voltages feeding the antennae and supplied by the transmitter E. The phase relationship between the feed voltage and the circulation currents should be: the same for the two radiating elements Al and AZ. This phase relationship is preferably chosen to be zero, since this condition corresponds to the maximum power radiated. The electricallength of the feed line of an antenna may be modified in any known manner. I

In another way, the dephasing between the feed voltages is maintained constant/for example, equal to 1r in the case of Fig. 4, by employing a crossed line of total length equal to half an operative wave-length. The dephasing :a necessary is then obtained by varying the impedance of the antenna Al by the control or manipulation of a' manipulation relay device Rel. The

length of the antenna Al is such that, the contact of relay Rel being closed, the current in the antenna AI has a phase advance (or a lag) a on the feed voltage. When the contact of relay Rel is opened, a reactance Z is introduced into the antenna and is of such value that the resultant reactance of the antenna is of inverse sign to the reactance when the relay contact is closed, a condition which produces a phase delay (or advance) or between the feed voltage and current in the antenna. and ot necessary to produce the interlocking of the radiated fields are obtained.

On account of the dephasing necessary in the antenna Al, the current in this antenna is weaker than the current in the antenna A2, tuned with no dephasing. The two guiding semi-axes are not then the one'an extension of the other. To rectify this and to bring the two semi-axes into line, the current in the antenna A2 is adjusted to equality with the current in the antenna AI by means of one or more resistances (or reactances) of adjustment and/or compensation, such as RI, R2, Fig.

In another way the reactances of both Al and A2 can be modified alternatively or simultaneous- 1y so as to obtain the desired successive dephasing. In this case each antenna comprises a-djusting. and/or compensation resistances or reactances RI and R2.

In these various directional antenna arrangements the spacing and dephasing of the elements are chosen to produce a unidirectional guiding, that is to say, if a vehicle proceding from y to ll Fig. 3, finds correct signalling, for example, by

additional signals usual in radio guiding systems,

the signalling will remain correct for the vehicle when the latter continues towards 11' after having passed the point ll. However, by varying the distance between the elements or the fixed dephasing, or both at once, the directional antenna de vices may be carried out so as to obtain two, four, or even a greater number of axes converging on the point I]. Whatever the number of guiding axes obtained, the narrowness of the guiding channel may be adjusted as desired by varying the absolute value,of the variable dephasing a.

In the drawings each of the elements Al and A2 has been considered as consisting of a simple conductor. This assumption has obviously only been adopted for the sake of simplicity and the invention is equally applicable to complex antenna systems comprising groups of antenna elements suitably associated as regards distance and adjusted as regards phase, of the exciting currents so as to provide directional properties.

Such units may be employed, for example, to increase the precision of the guiding along one or more concurrent axes in order to concentrate the energy radiated in a narrower dihedron and to prevent the radiation in particular directions or for still other purposes which may be desirable in radio-guiding systems.

Fig. shows an arrangement of a directional antenna system for radio guiding of aeroplanes, for instance, for blind landing. In this drawing the transmitting station feeds, by means of a transmission line 2, two groups of antennae 3 and 4 arranged on each side of a landing ground 5. The transmission line 2 is indicated in dotted lines to show that it has no part capable of encumbering said landing ground 5. For example, this line may consist of a transmission line by underground cable. A transmission network or artificial dephasing line 6 is shown inserted in the line.

In this way the two dephasings +04 l The distance between the two radiating groups is determined according to the operative wavelength chosen and the dimensions of the landing ground itself. This distance may vary from an amount in the vicinity of A of the operative wavelength to about one operative wavelength. In a preferred embodiment of the invention this distance is taken equal to half an operative wavelength in the air. The real length of the transmission line is generall taken substantially equal to this distance for reasons of economy, but the electrical length of this line, on account of the difference of the speeds of propagation in the air and in the cable transmission line, is not equal to half a wave-length. In order to obtain this equality the dephasing network 6 or artificial line is inserted in the transmission line 2 and adjusted so that the two groups of antennae are fed with exciting currents having an initial dephasing of in this case. As explained hereinbefore, the radiation diagram of the two radiating groups will then comprise two circular tangential diagrams having as respective centres the electrical centres of the radiating groups.

An alternate periodic dephasing is then introduced into the energy fed to the radiating groups, as hereinbefore explained, so as to produce the directive axis Hi. This dephasing might be obtained by modifying the electrical length of the radiating groups. However, in view of the distance between the groups of antennae the manipulation of the radiating groups themselves, which would give the desired additional alternate dephasing, would be practically impossible and such dephasings would be obtained by modifying the electrical length of the transmission line 2 connecting the radiating groups. This manipulation can be obtained directly on the transmission line 2, Fig. 5, or on the transmission lines 2 and 2', Fig. 6, but in accordance with a feature of the invention these dephasings are obtained by modifying the artificial line 6, Fig. 5, or the artificial lines 6 and 6, Fig. 6. This modification may be made either to the whole of the artificial line 6, or to a portion only of this line.

In any case, the desired electrical length of the transmission line between the antennae will preferably be established by means of one or more dephasing networks such as 6, once the said line has been constructed in accordance with the local conditions (ground, economy, etc.

Fig. 6 shows the case in which the two groups of antennae 3 and 4 instead of being fed by a common transmission line from the transmitter i are fed by two separate transmission lines 2 and 2, each comprising a dephasing network or artificial line 6 and 6 respectively. The operation of such a device will be the same as that explained with regard to Fig. 5, the manipulation taking place on the two dephasing networks 6 and 6 simultaneously, or on one of them only.

The distance between the two radiating groups, which has been described as being half a wavelength in the air of the operative wave, is obviously not a critical distance, and any distance comprising, for example, between A; and a whole wavelength approximately may be employed in accordance with the practical conditions of installation of the radio-guiding system. The electrical length of the transmission line can always be made equal if desired to half an operative wavelength by means of an artificial line so as to preserve an initial dephasing of 180 between the radiation of the two groups. Or rather, any desired initial dephasing may be obtained for the production of directive axes at any desired angle with respect to the axis of symmetry of the two groups of radiating elements.

The initial regulation of the artificial network in order to determine the initial phase difference between the radiations from the antennae can be modified subsequently in order to enter the guiding axis or channel angularly. This axis or channel could thus be brought to any direction between and 360 by this simple adjustment so as successively to obtain temporary guiding axes of diiferent directions, while only employing the two antennae or groups of antennae existing in the installation and without material modification of these antennae or groups of antennae.

The antenna structure of each group will be determined in terms of the radio-guiding conditions to be fulfilled. For example, in order practically to eliminate a lateral radiation of the system the two groups of antennae may be composed of frame aerials. In order to eliminate a backward radiation each group may be composed of a frame aerial and a vertical conductor, or by a set of conductors having this desired directional characteristic. One of the groups may be composed of a frame aerial and the other of a vertical conductor in order to obtain an inclined radiation channel. In a general manner the structures of the two groups of directional antennae will be provided so as to obtain radiation diagrams only concerning the useful portions of the space.

Fig. 7 shows more particularly the arrangement of Fig. 6 applied to an airport. Although the system has hitherto been described in the case of guiding aeroplanes, however, it is clear that the invention may also equally be employed to guide boats through navigable channels, for example, into sea-ports as indicated in Fig. 8. A group of directional antennae, such as 3 or 4, referred to above are arranged on each side of the channel at the ends of the jetties, for example, and the two groups are joined by a submerged cable 2, the transmitter itself I being situated on either side of the channel, or at a distant point. The guiding axis ID will then pass through the channel.

Submersible vessels can also be guided when submerged in accordance withthe method of guiding of the present invention. In this case the radiator groups 3 and 4 will be replaced by ultra-sound oscillators and projectors which can be submerged on either side of a channel in order to supply the same directional effects as the groups of surface antennae.

The invention is obviously not limited to the embodiments described and shown, but on the contrary is capable of numerous modifications and adaptations without departing from its scope as defined in the appended claims.

What is claimed is: 7

1. A radio system for guiding vehicles comprising a pair of radiating antennae arranged in' spaced relation, a source of high frequency current, transmission lines connected to supply exciting currents from said source to said pair of radiating antennae, and means for alternately varying the impedance of one of said radiating antennae to render-the resultant reactance of said antenna alternately positive and negative, while maintaining a continuous flow of power from said transmission line to said one antenna, whereby the waves radiated from said one antenna are alternately de-phased to opposite sides of the phase of the radiated wave which would be obtained in case the resultant reactance of said one antenna were zero.

2. A radio system according to claim 1 wherein the exciting currents supplied to said pair of radi.. ating systems are supplied over transmission lines of equal length and one line is reversed with respect to the other.

JULIEN JEAN BAPTISTE LAIR. GEORGES EDME MARCEL PERROUX. 

